Build Your First Decision Function
Learning objectiveReturn a simple legal action without guessing raise sizes.
Understand the idea
Start with the legal object, not a memorized action list. Checking is free; calling pays chips; folding gives up the hand. A beginner rule can cap calls at a small number of chips, then fold. This is a teaching baseline, not a profitable strategy.
A raise is legal only if legal.raise is true and its total target is an integer between minTo and maxTo. Leave betting out of your first function. Once tests cover check, call, and fold, add a separately tested raise branch.
At the poker table
Facing 40 chips with a 1,000-chip stack, this example folds because the cap is 20. Facing a free check, it checks.
Code and decision sketch
Pythondef choose(observation):
legal = observation.get('legal') or {}
if legal.get('check'):
return {'kind': 'check'}
if legal.get('call') and legal.get('callAmount', 0) <= 20:
return {'kind': 'call'}
if legal.get('fold'):
return {'kind': 'fold'}
raise ValueError('No supported legal action; inspect observation')Common mistake
Do not send {'kind':'raise','to':20} merely because you want to add 20 chips. The target is the seat's total bet, and the legal bounds are authoritative.
Try it yourself
Write three observations that trigger check, call, and fold. Verify the returned kind is marked true in legal.